Astronomical periods and weights for tracking, for any age — astro_periods

Returns the main eccentricity, obliquity and precession periods with weights proportional to their typical amplitude, for use in track_astro_hmm. The obliquity and precession periods follow from the precession constant k at the given age (AstroGeo22, via astro_terms) or from a k given directly (e.g. estimated with test_tuned), so that the periods fit deep-time records such as the Silurian and Devonian. The eccentricity periods are the La2004 values; the 405 kyr period is stable through the Phanerozoic, the short eccentricity periods are less certain before about 60 Ma.

Usage

astro_periods_tracking(
  age_ma = 0,
  k_yr = NULL,
  include = c("eccentricity", "obliquity", "precession")
)

Arguments

age_ma: Age of the record in Ma (numeric, >= 0); the precession constant, and with it the obliquity and precession periods, are taken from the AstroGeo22 solution at this age (passed to astro_terms). Ignored for the precession constant when k_yr is given. Default=0 (present-day periods).
k_yr: Optional precession constant (numeric, single value) used instead of the AstroGeo22 value for age_ma, given as the period of the axial precession in years (passed to astro_terms, which converts it to arcsec/yr as 360 * 3600 / k_yr), e.g. estimated with test_tuned; NULL uses AstroGeo22. Default=NULL.
include: Which families of cycles to return (character vector, any of "eccentricity", "obliquity", "precession"). When only "eccentricity" is included, the 405-kyr cycle gets weight 1 (instead of 0.5): in records in which only the eccentricity is resolved, the stable 405-kyr cycle carries the age model. Default=c("eccentricity", "obliquity", "precession").

Value

A data frame with term, family, period (kyr) and weight.

Examples

astro_periods_tracking(0)
#>     term       family    period weight
#> 1  g2-g5 eccentricity 405.69120    0.5
#> 2  g4-g2 eccentricity 123.85321    0.3
#> 3  g3-g2 eccentricity 130.69786    0.2
#> 4  g4-g5 eccentricity  94.88563    0.3
#> 5  g3-g5 eccentricity  98.85170    0.2
#> 6   k+s3    obliquity  40.98966    1.0
#> 7   k+s4    obliquity  39.61761    0.4
#> 8   k+s6    obliquity  53.73163    0.3
#> 9   k+g5   precession  23.68197    1.0
#> 10  k+g2   precession  22.37580    0.8
#> 11  k+g4   precession  18.95188    0.6
#> 12  k+g3   precession  19.10498    0.4
astro_periods_tracking(420)        # Silurian
#>     term       family    period weight
#> 1  g2-g5 eccentricity 405.69120    0.5
#> 2  g4-g2 eccentricity 123.85321    0.3
#> 3  g3-g2 eccentricity 130.69786    0.2
#> 4  g4-g5 eccentricity  94.88563    0.3
#> 5  g3-g5 eccentricity  98.85170    0.2
#> 6   k+s3    obliquity  30.49676    1.0
#> 7   k+s4    obliquity  29.73069    0.4
#> 8   k+s6    obliquity  37.03020    0.3
#> 9   k+g5   precession  19.75496    1.0
#> 10  k+g2   precession  18.83767    0.8
#> 11  k+g4   precession  16.35077    0.6
#> 12  k+g3   precession  16.46460    0.4